High performance motorcycle

ABSTRACT

A high performance motorcycle having a frame, engine suspension, and rear wheel drive system that enables rider foot positioning close to the longitudinal centerline of the motorcycle and an overall aerodynamic profile. The engine suspension, centering and damping system allows for lateral movement while damping vibration and unwanted oscillations. The rear wheel drive includes a driven pulley axially disposed on a rear wheel axle, a drive pulley configured to receive motive output from the motorcycle engine, an idler pulley disposed above a line between the axes of rotation of the drive pulley and the rear wheel axle, and a belt or chain disposed around and operatively connecting the drive pulley, the driven pulley and the idler pulley, wherein the idler pulley and the drive pulley configured so as to provide substantially constant tension to a belt or chain over the range of travel of the rear suspension.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a divisional of U.S. Utility patentapplication Ser. No. 15/296,808, filed Oct. 31, 2016 (Oct. 31, 2016),which in turn is a divisional of U.S. Utility patent application Ser.No. 14/216,994, filed Mar. 17, 2014 (Mar. 17, 2014), now U.S. Pat. No.9,469,363, issued Oct. 18, 2016 (Oct. 18, 2016), which claims thebenefit of U.S. Provisional Patent Application Ser. No. 61/788,988,filed Mar. 15, 2013 (Mar. 15, 2013).

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

THE NAMES OR PARTIES TO A JOINT RESEARCH AGREEMENT

Not applicable.

INCORPORATION BY REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not applicable.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to motorcycles, and moreparticularly to high performance motorcycles, and still moreparticularly to a lightweight aerodynamic motorcycle frame design havingimproved cornering and handling characteristics, an improved and saferframe configuration for a rider's feet, an engine suspension systemcapable of damping frame oscillations, and a rear suspension system thatprovides constant belt tension and exhibits constant anti-squatcharacteristics.

Background Discussion

Motorcycle designs are both art and engineering. Nothing delights theinformed eye more than seeing mechanical and aerodynamic advantageembodied elegantly. That is what engineers and designers workingcollaboratively in the motorcycle world endeavor to achieve. Thus, theever astounding futuristic designs rolled out annually by the majormanufacturers are nothing if not high performance fashion statements.Simply put, they are beautiful. Yet, over the years improvements inperformance have lagged behind improvements in design, and there remainmany motorcycle performance characteristics calling for improvement. Inshort, the art is not perfected. The present invention is therefore notstingy in that regard, as it provides numerous advances in the art, andthus numerous advantages in design. They are described in detail herein.

BRIEF SUMMARY OF THE INVENTION

The present invention is an improved high performance motorcycle design.

It is first and principal object of the present invention to provide anew and improved motorcycle design that allows increased lean anglebefore making road contact with the foot pegs/plates or with the rider'sfeet.

It is another object of the present invention to provide a new andimproved motorcycle design that allows a lower rider position andtherefore a lower overall center of gravity of the rider and motorcyclein combination.

It is another object of the invention to provide a motorcycle designwith reduced frontal area and concomitantly improved aerodynamiccharacteristics including reduced wind resistance and drag.

It is another object of the present invention to provide a motorcycledesign having a final drive belt/chain held in constant, effectivelyunchanging tension.

Yet another object of the present invention is to provide an improvedmotorcycle design that dampens natural motorcycle modes of oscillationdetrimental to performance.

A still further object of the present invention is to provide amotorcycle design having foot and leg protection for a rider to reduceinjuries due to side impacts.

A further object of the present invention is to provide a motorcyclehaving a frame, fuel tank, and seat unified and combined in a monocoquedesign to reduce weight.

Another object of the present invention is to provide a motorcycledesign having a very lightweight and low cost rear suspension withconstant anti-squat characteristics while also providing constant beltor chain tension.

A still further object is to provide a motorcycle design having improvedtraction when hitting bumps in turns at large lean angles.

Yet another object of the invention is to provide a motorcycle having anengine and transmission that can be rapidly and easily removed with aminimum disturbance to of other vehicle parts, thereby reducingmaintenance time and costs.

The foregoing summary broadly sets out the more important features ofthe present invention so that the detailed description that follows maybe better understood, and so that the present contributions to the artmay be better appreciated. The additional features of the invention thatwill be described in the detailed description of the preferredembodiments of the invention will form the subject matter of the claimsappended hereto.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

The invention will be better understood and objects other than those setforth above will become apparent when consideration is given to thefollowing detailed description thereof. Such description makes referenceto the annexed drawings wherein:

FIG. 1 is right side view in elevation of the high performancemotorcycle of the present invention, showing the position of a riderproperly seated for travel at speed;

FIG. 2 is a front view in elevation thereof;

FIG. 3 is an upper rear left perspective view thereof;

FIG. 4A is an upper left rear perspective view of the engine featuringits mounting and suspension system;

FIG. 4B is an upper left rear perspective view of an alternative enginemounting and suspension system;

FIG. 5 is a lower right perspective view showing details of theengine/motor lateral motion centering spring and damper;

FIG. 6 is an upper front left perspective view of the gear box andclutch;

FIG. 7 is a right side view in elevation showing the inventivemotorcycle with the engine and drive train removed so as to highlightthe rear suspension, select elements of the overall configuration, andto provide a template for locating the driving and idler pulleys so asto ensure constant belt tension and anti-squat characteristics areachieved;

FIG. 8 is a bare sketch or schematic overlay of FIG. 7 comprising theconstruction lines for commencing the suspension design process;

FIG. 9 is a sketch of FIG. 7 showing construction line locations if therear wheel is dropped (lowered) 33% of total suspension travel;

FIG. 10 is the same bare sketch of FIGS. 8 and 9 showing theconstruction lines if the rear wheel is elevated 33% of total suspensiontravel;

FIG. 11 is the sketch of FIG. 10 superimposed on the sketch of FIG. 9,and including construction circles employed to locate the idler anddriving pulleys;

FIG. 12 is an upper left rear perspective view of the rear suspension ofthe present invention, shown attached to the rear portion of themotorcycle frame;

FIG. 13 is a lower left perspective view thereof;

FIG. 14 is a right side view in elevation of the rear portion of theinventive motorcycle showing how the procedure for achieving constantbelt tension and anti-squat characteristics can be achieved using aconventional swing arm;

FIG. 15 is an upper left rear perspective view thereof;

FIG. 16 is a lower right perspective view thereof;

FIG. 17 is an upper left front perspective view of the bare frame of thepresent invention;

FIG. 18 is a lower left rear view thereof;

FIG. 19 is an upper right rear view thereof; and

FIG. 20 is a front view in elevation of a rider in the aerodynamicposition made possible by the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 through 19, wherein like reference numerals referto like components in the various views, there is illustrated therein anew and improved high performance motorcycle. Looking first at FIGS. 1through 3 and FIG. 6, there is illustrated therein a new and improvedhigh performance motorcycle. FIGS. 1-3 illustrate a first preferredembodiment of the motorcycle, showing that the inventive vehicleincludes a monocoque frame 1, having a front portion 1 a with a headtube 1 b, a seating portion 1 c, and a rear portion 1 d. A rider 2 isshown in a proper position for forward travel at speed. However, theframe is shown without either a seat or fuel tank mounted on the frame.

Rotatably coupled to the frame head tube 1 b is a conventional frontsteering and suspension system, including telescopic front forks andsuspension 3 a, a front wheel 3 b, and a steering head 3 c. Left andright handle bars and grips 4 a, 4 b, are connected to the lower portionof the steering head in a well-known manner, so as to bring the rider'supper body into a lowered, aerodynamic position on the motorcycle,especially evident in FIGS. 2-3.

Engine or motor 7 (“engine” herein) is mounted to the underside 1 e ofthe front portion 1 a of frame 1 and is positioned so as to be locatedin front of and below the rider's shins 2 a. The engine is shown sizedas a typical inline 2-4 cylinder motorcycle engine crankcase, block, andhead. It is shown as a “box,” both suggesting the variations possible inthe power source and the fact that the engine may be in an enclosed orcompartment. It will be understood, therefore, that the “engine”employed in the present invention could be many kind of power source forconverting energy to motion and made suitable for use in motorcycles,including, but not limited to V-type engines, electric motors withbattery packs, flywheel systems, and so forth. The term “engine” as usedherein also includes basic engine components, such as pumps, generators,induction systems, exhaust systems, heat exchangers, superchargers,electronics, and the like.

Power from the engine is communicated to the rear wheel through theinventive drivetrain, which includes a clutch 8, located on the rearside 7 a of engine 7, and a conventional, linearly adjustable two-piecespline slip joint drive shaft 9 disposed substantially on thelongitudinal centerline of the motorcycle and having front and rear endU-joints 9 a, 9 b, respectively. The spline slip joint permits a degreeof length adjustment, which is needed to accommodate engine lateralmotion (discussed more fully below). The rear end U-joint 9 b is coupledto the input shaft coupler 10 a of the input shaft assembly (details notshown) in gear box 10 (see FIG. 6). The clutch 8 a, as will beappreciated, may be collocated with the gear box, rather than disposedon the engine housing at the front end of the drive train. Locating theclutch on the engine (see FIG. 1) simplifies the gear box design of thekind described next.

The drive train is a single or multi-speed gear box with an outputpulley 11 operatively coupled through belt or chain 12 over idler pulley13 to rear wheel (driven) pulley 41 coaxially disposed on the hub oraxle of rear wheel 15. The system couples the drive shaft 9 to theoutput pulley 11 through a clutch and multi-speed gear system. The driveshaft and output pulley are oriented normal to one another, and the gearbox thus reorients the input drive shaft rotation through a gearassembly (bevel gear set) to a lateral shaft and gear assembly of a kindknown in the art. The kind of gear box employed in the motorcycle istherefore not limiting as there are numerous design choices possible forthis system. In a possible design choice, the gear box could beorganized around an upper transverse shaft on center with the drivingpulley and a lower transverse shaft in the plane of the input shaft andbevel. A conventional multi-speed gear “cluster” would couple the upperand lower shafts.

Referring next to FIG. 4A and FIG. 5, details are shown of how engine 7is mounted to, and suspended under, the underside 1 e of the frontportion 1 a of the frame 1 using front and rear low friction lateral(linear) slides 6 a, 6 b. The linear slides are configured as elongatemale dovetail elements that insert slidingly into integral or weldedmotor mounts 1 f, 1 g, having complementary female dovetail channels.Motor/engine mounting is completed using a motor lateral motioncentering spring and damper 5 disposed between a mounting bracket 1 h onthe front portion of the underside of the frame 1, and an engine-sideball-and-joint coupling 6 c. The centering spring and damper assemblykeeps the engine centered. Yet, as will be readily appreciated from theviews, the linear slides permit lateral translation of the entire enginewhen the motorcycle is subjected to lateral accelerations. The springand damper assembly has a centering and a damping effect on any enginemotion. The linear slides help isolate engine vibration and reduce thedegree to which it is conducted to the rider; lateral motion of theengine absorbs shock and adds damping when the motorcycle travelsthrough turns, and damps the wobble and weave modes of oscillationcharacteristic of motorcycles. While in a preferred embodiment theslides are configured in triangular dovetails, any of a number ofsuitable configurations could be employed to provide the kind of slidingsuspension achieved in this design. Alternatives might include, forinstance, T-shaped male elements. Further, it will be appreciated thatthe relative (top/bottom) positions of the male and female elementscould be reversed.

In the alternative, and now referring to FIG. 4B, the engine can bemounted to the frame using a combination of parallel links thataccomplish the same objective as the linear slides but with potentialcost and weight savings. As with the linear slides described above, thissystem of parallel links prevents the engine from rotating relative tothe frame. In this preferred alternative embodiment, the centeringspring and damper assembly is identical to that used with the linearslides, but rather than transversely oriented slide elements, twomounting tabs 22 a, 22 b, are affixed to the underside of the frame 1 atthe rear portion 7 a of the engine 7. The engine is then suspended fromthe frame using: first, two parallel longitudinally oriented axial links20 a, 20 b, each pivotally affixed at a forward ball joint 20 a′, 20 b′,and at a rear ball joint 20 a″, 20 b″ on tabs 22 a, 22 b, respectively;and second, two parallel vertically oriented axial links 20 c, 20 d,connected at a lower ball joint 20 c′, 20 d′ and at an upper ball joint20 c″, 20 d″ on tabs 22 b, 22 b. In this way, the engine is allowed totranslate laterally a short distance as described with respect to thefirst preferred embodiment. When a parallel link system is employed forengine suspension, a conventional fixed length drive shaft 21 withU-joints at each end is also used. The length of the drive shaft 21preferably matches that of the longitudinally disposed parallel axiallinks 20 a, 20 b. In yet another alternative, the arrangement ofparallel links can be accomplished with flexible links operating likeleaf springs arranged in parallel rather than using rigid ball jointlinks.

The rear portion of the motorcycle is characterized by a novel andadvantageous rear suspension system that includes dual (right and left)struts or braces preferably configured as triangular arms or frames 16a, 16 b. Right and left triangular arms may be connected with atransverse brace or cross-member 16 c, which unifies the arms for easeof handling when the system is being assembled. The cross member is notrequired for correct suspension operation when fully assembled. Thetriangular arms 16 a, 16 b are pivotally connected at their lower endsto a fitting 16 a′, 16 b′, disposed on rear wheel axle bearing 15 a, 15b, and at their respective upper ends to the back of a cross-member 17,which is, in turn, pivotally connected at its front side to the rearportion 1 d of the frame 1 (see FIGS. 12-13 for details on theseconnections). The body of the cross-member is preferably generallycylindrical in shape, and as alternative, cross-member 17 may be adaptedfor insertion into a portion of the motorcycle frame such that the axisof rotation is the longitudinal axis of the cylindrical body. Right andleft adjustable length links 14 a, 14 b, are each connected to the frameand to a fitting axially disposed on a rear wheel axle bearing or afitting disposed on a bearing. A rear suspension spring and damper 19 ispivotally connected at the frame 1 and to the rotatable cross member 17.Other connections between the spring/damper assembly and the suspensioncomponents to support the weight of the motorcycle are possible. Theprincipal features of the system reside in the cross member, theA-frames, and the adjustable links.

Details of the mechanical elements of the rear suspension are betterappreciated by reference to FIGS. 12-13, where it is seen that right andleft triangular arms 16 a, 16 b are pivotally connected at their lowerends to fitting 16 a′, 16 b′, disposed on rear wheel axle bearing 15 b.They are pivotally connected at an upper end 16 a″, 16 b″ to the back 17a of a cross-member 17 on right and left mounting bracket pairs 17 b, 17c. Rotatable cross-member 17 is pivotally connected at its front side 17d to mounting bosses 1 j, 1 k at the rear portion 1 d of frame 1. Theright and left adjustable length links 14 a, 14 b, are connected toframe mounting points 1 l, 1 m with forward ball joints 14 a′, 14 b′ andto fittings 16 a′, 16 b′ with rear ball joints 14 a″, 14 b″. The leftrear suspension spring and damper 19 is pivotally connected at a lowerend 19 a to the mounting point 1 m on frame 1 and at an upper end 19 bto a mounting bracket 17 g on the front side 17 d of the rotatable crossmember 17. It will be understood that the riding characteristics of thepresent invention are best achieved by proper selection and tuning ofshock absorbers according to the precise use or uses to which themachine will be put. But a wide range of suitable coil spring andhydraulic shock options is contemplated. (Note: the anti-squatcharacteristic as used herein is not understood to be a function of thespring/damper response. Anti-squat means the rear suspension and beltsystem work together to produce a down force on the wheel as torque thatwould drive the motorcycle forward is generated on the wheel. This downforce counteracts some of the load transferred back to the rear wheeland reduces the suspension compression. See Foale reference below formore detail.)

FIG. 13 also shows L-shaped idler pulley mounting arm 13 a supportingidler pulley axle 13 b, the arm being disposed above and behind therider foot plate 1 n, which supports a rider's feet between right andleft side impact protection bars 18 a, 18 b (shown in several of theviews) that reduce a rider's leg injury in the event of a side impact.

The configuration shown in FIGS. 1-5 makes possible a significantlyimproved rider position. When looked at from the side (FIG. 1), therider position looks entirely conventional, but it is noticeablydifferent when viewed from the front and the upper rear (FIGS. 2 and 3,respectively), where it is seen that the rider's feet are movedsubstantially inwardly (toward the longitudinal center line of themotorcycle). On a conventional motorcycle, the rider's feet arepositioned outside the chain and swing arm, often making the feet thefirst part to hit the ground when leading the motorcycle/ridercombination. In consequence, the rider must be positioned higher on themotorcycle so as to prevent the feet from hitting the ground at high(but typically encountered) lean angles.

However, in the present invention, the drive shaft is selected and sizedto be long enough that it permits the rider's feet to be positioned onrider footrests located between the engine/motor and the gear box, andthus for each foot to be positioned proximate the center plane of themotorcycle. By moving the rider's feet inwardly, the configuration ofthe present invention permits the rider to assume a position that islower (overall) on the motorcycle, while at the same time preventingfoot-ground contact at high lean angles. This creates a more aerodynamicposition and a lowered center of gravity, and therefore better handlingand cornering and increased safety.

Exposing less of the rider's feet and lower legs to the airstream alsoreduces the aerodynamic drag. Although not shown, the reader shouldassume that conventional aerodynamic devices could be added to furtherimprove the aerodynamics of the inventive motorcycle. Examples of suchdevices include fairings, ducts, wind shields, fenders, spoilers,turbulators, etc., mounted to the frame, engine or suspensioncomponents.

However, another challenge facing the designer is the question of how toprovide for an appropriate “anti-squat” factor of the rear suspension.Ideally, the suspension displays a constant “anti-squat” factor over itsrange of travel. (For an explanation of the anti-squat factor, thereader is referred to Chapter 9 of Motorcycle Handling and ChassisDesign, self-published by Tony Foale, 2002, ISBN-10: 8493328618;ISBN-13: 978-8493328610.

As noted in the Summary, the advantages of the present invention are notlimited to an improved rider position. Rather, the present inventionalso provides an improved rear suspension that maintains a constant beltor chain tension while producing constant-anti-squat characteristics. Nopreviously designed suspension has exhibited both constant belt tensionand constant anti-squat factor at the same time. Until the presentinvention, it has not been understood or appreciated that the drivingand idler pulleys could be positioned to provide constant tension andconstant anti-squat characteristics at the same time where the idler islocated above a line drawn between the center of the rear wheel and thedriving pulley. The present invention includes such a method forachieving this advantageous positioning. This alone constitutes asignificant advancement in the state of the art of motorcycle design.

As suggested from the immediately preceding paragraph, theanti-squat/constant tension feature is achieved by correct positioningthe idler and driving pulleys, but the first step in the inventiveprocedure is to select the rear suspension dimension and attachmentpoints on the frame; following that the idler and driving pulley arelocated and configured according to an inventive procedure.

The following procedure sets forth the steps required to locate thedriving and idler pulleys such that the belt tension remainsapproximately constant over the range of suspension travel andsimultaneously provides a constant “anti-squat” characteristic.Reference should now be made to FIGS. 7-11.

Preliminarily, note should be taken that a designer of the motorcycle ofthe present invention has considerable flexibility in the details of therear suspension dimensions. For instance, the designer is free to choosethe lengths of key suspension members, including the adjustable lengthlink 14, the dual arm links 16 a, 16 b, and the rotatable cross-member17, along with attachment points 14 a′, 14 b′, 17 e, 17 f, 17 g, to theframe 1.

Once the designer has selected the suspension dimensions, the nextquestion is how to locate the idler pulley 13 and driving pulley 11, sothat the belt 12 will stay at constant tension over the travel of therear suspension.

Referring first to FIG. 7, which is a right side view in elevation ofthe inventive motorcycle including only the frame 1, front suspension 3,driven pulley 41, and rear suspension members 14, 15, 16, and 17. Inthis view, the front and rear suspensions are positioned in their centerof travel.

Next, a two-dimensional sketch is laid over the side view of FIG. 7 withvarious sketch lines corresponding to various suspension links and othercomponents of the bike. FIG. 7 shows the sketch superimposed on themotorcycle of FIG. 1, and FIG. 8 shows the bare sketch generated fromFIG. 7. A legend for the construction lines in each sketch of FIGS. 7-8includes

23—construction line corresponding to the road when the front and rearsuspensions are at the center of travel;

24—construction line passing through the center of the front wheel andhaving an arbitrary length;

25—construction circle corresponding to the front wheel at the center ofsuspension travel;

26—construction point at the end of construction line 24;

27—construction line starting at point 34 and passing through point 26;

28—construction line corresponding to adjustable link 14;

29—construction circle corresponding to rear wheel 15;

30—construction line corresponding to rotatable cross member 17;

31—construction line corresponding to a dimension on triangular arm 16;

32—construction circle corresponding to the driven pulley 41;

33—construction line corresponding to a dimension on the triangular arm16;

34—point at the bottom of construction circle 29.

The anti-squat fraction is determined by the length of construction line24. This length can be chosen arbitrarily within practical limits.

Next, and referring now to FIG. 9, there is shown the construction linelocations if the motorcycle rear wheel is assumed to be dropped fromcenter a distance of 33% of total suspension travel. The referencenumbers for the construction lines for each of the views of FIGS. 8-9are consistent. If a construction line does not move with thesuspension, it has the same reference number in each figure. If theconstruction line does move with the suspension in FIG. 9, it isrenumbered with the same number carried over from FIG. 8 with the addedsuffix of “N”.

From this it is seen that FIG. 9 contains four constructions not seen inFIG. 8. They include:

35—construction line from point 38N and tangent to construction circle32N;

36—construction line collinear with construction line 28N andintersecting construction line 27N at point 38N;

37—construction line from point 38N and tangent to construction circle32N;

38N—point at which an extension of construction line 28N would intersectconstruction line 27N.

Next, FIG. 10 shows the construction line locations if the rear wheel isassumed to be raised from center a distance of 33% of the totalsuspension travel. Reference numbers for the construction lines betweenFIGS. 8 and 10 are the same: If a construction line does not move withthe suspension, it bears the same reference number in each figure. Ifthe construction line does move with the suspension from FIG. 8 to FIG.10, the new line location in FIG. 10 bears the same numerical portion ofthe reference number and then includes the alphabetic suffice of “J”.Construction lines 35J-38J in FIG. 10 are correlated to constructionlines 35-38 in FIG. 9.

Next, FIG. 11 illustrates FIG. 10 superimposed on FIG. 9 and furtherincludes two circles as described as follows: Circle 39 is tangent toconstruction lines 37J and 37N. Its diameter and position correspond tothe correct position for the idler pulley 13. Its diameter can beselected arbitrarily within practical limits by the designer. Circle 40is tangent to construction lines 35J and 35N. Its diameter and positioncorrespond to the correct position for the driving pulley 11. Itsdiameter can also be selected arbitrarily within practical limits by thedesigner.

At this point the procedure for locating the idler pulley and the driverpulley is complete.

There is a special case that is contemplated and covered by the presentinvention. Referring again to FIGS. 7 and 8, the foregoing procedureapplies equally to the special case when the length of construction line33 is zero. This corresponds to the kinematics of a conventional rearswing arm for a motorcycle. The constant belt tension and constantanti-squat procedure can be used with a conventional swing armsuspension (see FIGS. 14-16). The spring and damper assembly 19 c cancomprise any arrangement of linkages and one or more spring and dampers,as is now common practice, and can attach at its lower end 19 d to theswing arm and at its upper end 19 e to the frame mounting point 1 k orother points. The conventional swing arm 42 can attach to the frame inthe general location shown in these figures, for instance on the sidesof mounting points 1 l, 1 m, or further forward in front of the rearwheel, also as is now common practice.

FIGS. 17-19 show the bare (monocoque) frame 1 of the present invention.These views feature the structural core of the inventive motorcycle, andcertain structural constraints (mounting points, most notably) arenecessary to support the inventive motor/engine mounting and rearsuspension design systems. However, departures from the preferredgeometry are possible and the inventive systems could be realized innumerous frame configurations, including those provided by a tubularspace frame. Nonetheless, a monocoque style is preferred. It may befabricated from sheet metal or composite materials. The frame structurewill generally extend from its head tube 1 b (pivot axis for steering)over the front wheel slightly aft the centerline to it rotatablecross-member mounting points over and slightly forward the centerline ofthe rear wheel. From the head tube 1 b the front portion 1 a of theframe slopes downwardly at its upper surface to a medial seating portion1 c generally level relative to ground plane in use, and then risesslightly to its rear portion 1 d, on which the rear suspension mounts.On the underside 1 e of the front portion of the frame is a generallyspace from which the engine is suspended, as described above. Behind theengine mounting area is a triangular trough 1 p having right and leftsides 1 q, 1 r that angle inwardly to create a space for the rider'sfeet on the foot rests provided by foot plate 1 n. The center of thebottom of the trough straddles the longitudinal centerline of themotorcycle. In length, the trough extends to a point roughly below thepoint at which the seat rises upwardly into the rear portion of theframe to the rotatable cross-arm mounting points 1 j, 1 k, the rearportion being of decreasing width or thickness as measured from top tobottom; in depth it extends downwardly from the medial (seat) portion ofthe frame to terminate in a trough bottom 1 t several inches above thedrive shaft 9, such that an open and empty space exists between thetrough bottom and the drive shaft. This enables a rider, whose feet areresting on the footplate 1 n, to touch his toes together.

The trough provides frame stiffness and structural rigidity, which arecritical insofar as it is the scaffold on which are connected, eitherdirectly or indirectly, the foot plate 1 n, the rear suspension lowermounting points 1 l, 1 m, the leg portion of the L-shaped idler pulleymounting arm 13 a, and the side impact protection bars 18 a, 18 b.

Referring finally to FIG. 20, there is shown a front view in elevationof the unique rider position made possible by the present invention;notably, the frame configuration, along with the drivetrain, rear wheeldrive configuration, and engine suspension. Note should be taken thatthe rider's feet are nearly touching, and this is how they arepositioned when the rider draws them inwardly to rest on the footplate.

What is claimed as invention is:
 1. A rear wheel drive system for amotorcycle having a frame, front suspension, front wheel, and steeringassembly connected to a front portion of said frame, an engine disposedin the front portion of said frame, a rear suspension having apredetermined range of travel, a rear wheel having an axle connected toa rear portion of said frame and operatively coupled to the rearsuspension, the rear wheel drive system comprising: a driven pulleyaxially disposed on the rear wheel axle; a drive pulley attached to saidframe and configured to receive motive output from the motorcycleengine; an idler pulley attached to said frame and disposed above a linebetween the axis of rotation of said drive pulley and the axis ofrotation of said rear wheel axle; and a belt or chain disposed aroundand operatively connecting said drive pulley, said driven pulley, andsaid idler pulley; wherein said idler pulley and said drive pulley areconfigured so as to provide substantially constant tension to said beltor chain over the range of travel of the rear suspension.
 2. The rearwheel drive system of claim 1, further including an elongate adjustablelink with connection structure for connecting said link between a rearwheel bearing and a motorcycle frame for fine tuning belt tension. 3.The rear wheel drive system of claim 1, wherein said driving and idlerpulleys are positioned so as to provide constant tension and constantanti-squat characteristics at the same time.
 4. A motorcycle rearsuspension comprising: an elongate rotatable cross member having a frontside and a rear side, said rotatable cross-member having connectionpoints for pivotal connection to a rear portion of a motorcycle frame;right and left suspension struts each having a lower end connected torespective right and left rear axle fittings adapted for coaxialplacement on said rear wheel axle, and an upper portion havingconnection points for pivotal connection to said rear side of saidrotatable cross member; and right and left length-adjustable linkshaving connection means for pivotal connection to said right and leftrear axle fittings, respectively, and to the motorcycle frame.
 5. Therear suspension of claim 4, wherein said suspension struts aretriangular frames.
 6. The rear suspension of claim 4, further includingconnection structure disposed on said front side of said cross memberfor connecting a spring and damper shock absorber between said crossmember and a mounting point on a rear portion of said motorcycle frameso as to support a portion of the weight of the motorcycle.
 7. The rearsuspension of claim 4, wherein said frame connection points on saidcross member are on front side of said cross member.
 8. The rearsuspension of claim 4, further including a rear spring and damperconfigured to support a portion of the motorcycle weight.
 9. A rearwheel drive system for a motorcycle having a frame, front suspension,front wheel, and steering assembly connected to a front portion of saidframe, an engine disposed in the front portion of said frame, a forkpivotally attached to the rear portion of said frame, a rear wheelhaving an axle pivotally connected to a rear portion of said fork, arear wheel drive system comprising: a driven pulley axially disposed onthe rear wheel axle; a drive pulley attached to said frame andconfigured to receive motive output from the motorcycle engine; an idlerpulley attached to said frame and disposed above a line between the axisof rotation of said drive pulley and the axis of rotation of said rearwheel axle; and a belt or chain disposed around and operativelyconnecting said drive pulley, said driven pulley, and said idler pulley;wherein said idler pulley and said drive pulley are configured so as toprovide substantially constant tension to said belt or chain over therange of travel of the rear suspension.
 10. The rear wheel drive systemof claim 9, wherein said driving and idler pulleys are positioned so asto provide constant tension and constant anti-squat characteristics atthe same time.
 11. The rear suspension of claim 9, further including arear spring and damper configured to support a portion of the motorcycleweight.